In such conventional gear selector devices two gear wheels are rotatably supported and spaced from each other on a transmission shaft. In addition, a sliding sleeve is non-rotatably and axially movably are supported between both gear wheels on the transmission shaft. By axial movement, the sliding sleeve can be brought to positive fit engagement with the first or the second gear wheel and thereby switch the transmission between the two ratio steps. The axial motion of the sliding sleeve is controlled by a shift fork radially acting from the outside upon the sliding sleeve. This solution implies a relatively large radial installation space, its construction cost is high and is susceptible to interferences.
From DE 37 11 490 C2 is known besides a gear selector device in which the sliding sleeve is axially moved not by a shift fork radially engaging from the outside but by means of a hydraulic device actuated from the inside, via axial holes extending within the transmission shaft. Thereby the radial height of this gear selector device is advantageously reduced. This solution thus has advantages regarding the weight and the number of mechanical parts needed. A disadvantage consists in there being provided in the transmission shaft holes for the pressurized oil and pistons actuated by an oil pressure for the axial movement of the sliding sleeve. That is relatively expensive functionally and requires a large shaft diameter.
In EP 1 055 835 A1 has further been disclosed a hydraulically actuated sliding sleeve supplied with control pressure from the interior of the transmission shaft and providing the hydraulic shifting device for the sliding sleeve outside the transmission shaft between two gear wheels so that the transmission shaft contains only the adequate axially extending supply holes for the oil pressure.
These two already known hydraulic actuation devices thus serve for axial displacement of the sliding sleeve of a selector transmission between two gear wheels as a rule disposed upon a transmission shaft. If several such arrangements of hydraulically actuated gear wheels and sliding sleeves, independent of each other, are located upon a transmission shaft, a relatively higher total cost results for the independent control of the individual sliding sleeves.
Therefore, the problem on which the invention is based is to reduce in such a gear selector device having several gear wheels and sliding sleeves associated with a transmission shaft, the construction cost needed for actuation of the individual sliding sleeves, the total weight and the susceptibility to interferences.